Refrigerating apparatus



March 5, 194() L. B. M. BUCHANAN REFRIGERATING APPARATUS Filed Aug. 5,1937 Zes/fea Bo Mo ffm l ATTOR- Y INVENTOR Buchanan c Patented Mar. 5,1940 UNITED STATESv PATENT QFFICE REFRIGERATING APPARATUS tion ofPennsylvania Application August 3, 1937 1o claims.

My invention relates to refrigerating apparatus and has for an object toprovide improved means for controlling the operation of such apparatus.

A' further object of the invention is to control the operation of atwo-temperature refrigerating lsystem by a single control mechanism.

It is still a further object of my invention to provide single thermalresponsive mechanism for controlling a two temperaturerefrigeratorwherel by the temperatures of the refrigerated zones aremaintained at different desired values.

It is another object of my invention to limit the maximum temperature ofthe media cooled by a refrigerator and the minimum temperature of thecooling element thereof.

These and other objects are effected by my invention as will be apparentfrom the following description and claims taken in connection with theaccompanying drawing, forming a part of this application, in which:

Fig. l of the drawing is a diagrammatic view of a two-temperaturerefrigerator controlled in accordance with my invention; and,

Fig. 2 is a view of a portion of the elements of 2t Fig. 1 rearrangedfor defining a second embodiment of the invention.

Reference will now be had to Fig. 1 of the vdrawing wherein the numeralI0 generally indicates a cabinet structure that defines relatively mihigh and low temperature zones or chambers III and l2 for the storageof' perishables. High and low temperature evaporators I3 and Ill ofsuitable construction are disposed within the zones for refrigeratingthe same and are supplied 35 with condensed refrigerant byl a condensingunit, generally shown at I5, and including a compressor I 6, driven byan electric motor II, and a condenser I. The latter is cooled in anywell known manner, such as, for example, by a fan I9.

it@ The refrigerating system which I have chosen to show has theevaporators I3 and I4 connected in series for the flow of refrigerant;the higher temperature evaporator I3 receiving condensed refrigerantfrom the condenser I8 through a conduit 2I and the refrigerant vaporizedin both evaporators being returned to the compressor I6 through asuction conduit 22. A suitable expansion device, such as a high sidefloat valve 23 50 may be connected in the conduit 2l for reducing thepressure of' the condensed refrigerant to the value maintained in theevaporator I3 by the compressorv I6. In order that the evaporators areoperated at different pressures and temperatures,

55 a restricting device, such as, for example, a capilterposed betweenthe evaporators I3andI-.I4 v

During operation vof the compressor I6, vaporized refrigerant atrelatively low pressure is withdrawn by thecompressor I6 from theevaporator 5 Ill and is compressed to a relatively high pressure. Thehigh pressure vapor is conveyed by a conduit to the lcondenser I8wherein it is cooled and condensed. Liquid refrigerant is conveyedthrough the conduit 2I to the evaporator I3, the 10 valve 23 reducingthe pressure of the liquid to the pressure of vaporizatlon in theevaporator I3. A portion of the liquid is vaporized in the evaporator I3and the remaining liquid and the gaseous refrigerant pass through therestricting de- 15 vice 2i to the low temperature evaporator I4.Vaporization of the liquid refrigerant is completed in the lowtemperature evaporator Ill at low pressure and temperature. Thedifference in temperatures of the two evaporators is obtained 20-v bythe restricting device 24 which effects a suitable difference invaporizing pressures.

In accordance with my invention, a single thermostat 26 having a thermalresponsive element or bulb 2l is employed for controlling the opera- 25tion of the condensing unit I5. The thermostat 26 operates to initiateoperation of the compressor I6 in response to temperature conditions inthe high temperature zone II and to terminate operation of the same inresponse to tem- 30 perature conditions in the low temperature zone,

I2. As shown, the low temperature evaporator I4 includes a loop orportion 28 that extends into the high temperature zone II and which isdisposed in heat ,transfer relation with the bulb 21. During inactiveperiods of the compressor I6, the evaporator portion 28 is heated by theair in the zone II to a value substantially equal to 'the temperature ofthe high temperature evaporator I3. During operation of the compressor40 I6, the evaporator portion 28 is depressed to the temperature of thevevaporator I4. Accordingly, the thermostat 26 operates to initiateoperation of the compressor I6 in response to a predetermined highternperature of the higher temperature evaporator I3 and to terminateoperation of the compressor in response to a predetermined lowtemperature of' the low temperature evaporator I4. As the portion 28 ofthe evaporator I 4 is relatively small, it has but little cool- 50 ingeffect on the higher temperature air in the zone Il. l

The thermostat 26 is of the conventional gas type and includes a bellows29 connected by a tube 3l to the bulb 2l.l The bellows 29 actuates 65 alever 32 and is biased by a spring 33 that may be adjustedby anadjusting screw 34. A movable switch member is connected to the lever 32by a snap-acting over center spring 36 and is engageable with astationary adjustable contact 31. 'Ihe contacts 35 and 31 are connectedin an electrical circuit 38 for controlling energization of the motorI1. The adjusting screw 34 is made accessible to the operator anddetermines the temperatures at which the motor I1 is started andstopped. By adjusting the contact 31, the temperature dierential or thedifference between the temperatures at which the motor is started andstopped, may be varied.

Operation As shown in the drawing, the motor `I1 and compressor I6 areidle as the switch contacts 35 and 31 are disengaged, the temperature ofthe bulb 21 being below the value a't which the thermostat 26 startsoperation. Accordingly, the temperatures of the evaporators I3 and I4are increasing due to the heat load in their respective compartments.'Ihe temperature of the portion 28 of the low temperature evaporator I4increases faster than the remainder of the evaporator I4 as it issubjected to the relatively high temperature of the air in thecompartment II and attains a temperature substantially equal to thetemperature of the evaporator I3. When the temperature of the bulb 21increases to a value of say 35, the thermostat 26 eects engagement ofthe contacts 35 and 31 for starting operation of the compressor I6.vaporization of refrigerant in both evaporators I3 and I4 is initiatedand both of the zones II and I2 are cooled.

The pressures of vaporization are progressively depressed in bothevaporators I3 and I4. The temperature of the evaporator portion 28 isdepressed to a value substantially equal to the remainder of theevaporator I4 and when a predetermined low value of say 5 F. isobtained, the thermostat 26 operates to terminate operation of thecompressor I6. At this time, the temperatureof the higher temperatureevaporator I3 is at a higher value of approximately 25 F. due to thehigher vaporizing pressure effected by the restricting device 24.

During the inactive periods of the compressor I6, the pressure of therefrigerant in the evaporators I3 and I4 tends to equalize whereby thetemperature of the low temperature evaporator I4 would be increasedsomewhat by the condensing of gas discharged from the higher temperatureevaporator. As the media in the zone I2 is at a relatively lowtemperature, the increase in temperature of the evaporator I4 is not asrapid as the temperature increase of its portion 28 or of the hightemperature evaporator I3.

Description of Fig. 2

In Fig. 2, I have shown a second embodiment of my invention that issimilar to the embodiment shown in Fig. 1 except that the hightemperature evaporator I3 is disposed in heat transfer relation with thelow temperature evaporator portion 28. The thermostat bulb 21 isattached to the evaporator portion 28 and is responsive to thetemperature thereof. In this embodiment, the temperature of theevaporator portion 28 attains, substantially, the temperature of theevaporator I3 during inactive periods of the compressor so that thelatter is started in response to the temperature of the high temperatureevaporator I3. As the temperature of the evaporator portion 28 andthermostat bulb 29 attain, substantially, the temperature of the lowtemperature evaporator I4 during active periods of the compressor, thelatter is stopped in response to the temperature of the low temperatureevaporator I4.

The condensing unit I5 and thermostat 26 of Fig. 1 are not shown in Fig.2 but it will be understood that these elements are connected to theconduits 2I, 22 and 23 in the manner shown in Fig. 1. Elements common toboth. embodiments are shown by similar reference characters.

Operation-Jig. 2

During active periods of the condensing unit I5, vaporization ofrefrigerant is eiected in the evaporators I3 and I4 at relatively highand low pressures, respectively, as described, heretofore. 'I'hetemperature ofthe bulb 21 and the evaporator portion 28 is depressed,substantially, to the temperature of the low temperature evaporator I4and, when a value of say 5 is attained, the condensing unit I5 isstopped.

The temperatures of the evaporators I3 and I4 increase during the shutdown period due to the heat loads thereon, the temperature of theportion 28 of the low temperature evaporator I4 and the bulb 21increasing rapidly andv attaining the temperature of the hightemperature evaporator I3. Operation of the condensing unit is initiatedwhen the temperature of the bulb 21 has been increased to a value of say35 F.

It will be apparent from the foregoing that the operation of bothsystems is similar. In Fig. 1, the evaporator portion 28 attains,substantially, the same temperature as the evaporator I3 during inactiveperiods of the compressor as both are subjected to the temperature ofthe air in the chamber II. In Fig. 2, the same result is obtained forthe same reason and further by the direct exchange of heat between theseelements.

Another embodiment of my invention is disclosed and claimed in mycopending application, Serial No. 243,279, filed November 30, 1938, andassigned to the assignee of the present application, said copendingapplication having claims therein which are generic to all embodimentsof both applications.

It will be apparent from the foregoing that I have provided improvedrefrigerating apparatus wherein a single control may be employed forcontrolling the temperature in both compartments of atwo temperaturemachine.

While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modications without departing from thespirit thereof,' and I desire,

therefore; that only such limitations shall be placed thereupon as areimposed by the prior art or as are specilcally set forth in the appendedclaims.

What I claim is:

1. In refrigerating apparatus, the combination of means definingrelatively low and high temperature zones to be refrigerated, means forrefrigerating the zones including rst and second evaporators associatedwith the respective zones, one of said evaporators having a relativelysmall portion thereof disposed in heat transfer relation with the mediabeing cooled by the other of the evaporators, and a thermostatresponsive to the temperature of said evaporator portion for controllingthe operation of the refrigerating means.

2. In refrigerating apparatus, the combination of means defining rst andsecond zones to be refrigerated, relatively low and high temperatureevaporators associated with the first and second Zones, respectively,means for circulating refrigerant through the evaporators, said lowtemperai ture evaporator having a relatively small portion thereofdisposed in heat transfer relation with refrigerant through saidevaporators, said low temperature evaporator having a relatively smallportion thereof extending into the air in the higher temperature zone,and means responsive to the temperature of said evaporatorA portion forcontrolling the operation of said compressor.'

4. In refrigerating apparatus, the combination of means definingrelatively low and high temperature zones to be refrigerated, low andhigh temperature evaporators disposed for cooling the respective low andhigh temperature zones, means for circulating refrigerant through theevaporators and effecting vaporization in the low and high temperatureevaporators at relatively low and high pressures, respectively, andthermal responsive means for controlling the operation of therefrigerant circulating means and disposed in heat transfer relationwith the low pressure refrigerant and the media cooled by the higherpressure refrigerant.

5. In refrigerating apparatus, the combination of means definingrelatively low and high temperature zones to be refrigerated, low andhigh temperature evaporators disposed for cooling the respective low andhigh temperature zones, means for circulating refrigerant through theevaporators and effecting vaporization in the low and high temperatureevaporators at relatively low and high pressures, respectively, andthermal re. sponsive means for controlling the operation of therefrigerant circulating means, said thermal responsive means beingresponsive, primarily, to the temperature of the media cooled by thehigh temperature evaporator for initiating operation of the refrigerantcirculating means and responsive, primarily, to the temperature of therefrigerant evaporated at relatively low pressure for terminatingoperation of the refrigerant circulating means.

6. In refrigerating apparatus, the combination of a cabinet structuredefining rst andsecond zones to be refrigerated, relatively low and hightemperature evaporators connected in series for the iiow of refrigerantand disposed, respectively, for cooling the first and second zones,means for circulating refrigerant through the evaporators, a device forcontrolling the flow of refrigerant from one evaporator tothe other andfor effecting said high temperature evaporator, and means disposed inheat transfer relation with said portion of the low temperatureevaporator for controlling the operation of the refrigerant circulatingmeans.

7. In refrigerating apparatus, the combination of a cabinet structuredefining first and second zones to be refrigerated, relatively low andhigh temperature evaporatorsconnected in series for the flow ofrefrigerant and disposed, respectively, for cooling the first and secondzones, means for circulating refrigerant through the evaporators, adevice disposed intermediate the evaporators for controllingvaporization of refrigerant in v the evaporators, said low temperatureevaporator having a portion thereof disposed in heat transfer relationwith the media cooled by said high temperature evaporator, and meansdisposed in heat transfer rel-ation with said portion of the lowtemperature evaporator for controlling the operation of ,the refrigerantcirculating means.

8. In refrigerating apparatus, the combination of a; cabinet structuredefining first and second zones to be refrigerated, relatively low andhigh temperature evaporators connected in series for the :dow ofrefrigerant and disposed, respectively, for cooling the first and secondzones, means forcirculating refrigerant through the evaporators, adevice having an elongated passage of fixed flow area for refrigerantand disposed intermediate the evaporators, said low temperatureevaporator having a portion thereof disposed in heat transfer relationwith the media cooled by said high temperature evaporator, and meansdisposed in heat transfer relation with said portion of the lowtemperature evaporator for controlling the operation of the refrigerantcirculating means.

9. In refrigerating apparatus, the combination of means defining firstand second zones to be refrigerated, relatively low and high temperatureevaporators associated with the first and second zones, respectively,means for circulating refrigerant through the evaporators, said lowtemperature evaporator having a relatively small portion thereofdisposed in heat transfer relation with the higher temperatureevaporator, and means responsive to the temperature of said evaporatorportion for controlling the operation of the refrigerant circulatingmeans.

10. In refrigerating apparatus, the combination of means defining rstand second zones to be refrigerated, relatively low and high temperatureevaporators associated with the rst and second zones, respectively, acompressor for circulating refrigerant through the evaporator, said lowtemperature evaporator having a relatively small portion thereofdisposed within the high tempera- ,ture zone, and thermal responsivemeans disposed in heat transfer relation with said evaporator portionand the high temperature evaporator for controlling the operation ofsaid compressor.

LESLIE B. M. BUCHANAN.

